CN113510695A - Robot joint position control method - Google Patents
Robot joint position control method Download PDFInfo
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- CN113510695A CN113510695A CN202110420487.9A CN202110420487A CN113510695A CN 113510695 A CN113510695 A CN 113510695A CN 202110420487 A CN202110420487 A CN 202110420487A CN 113510695 A CN113510695 A CN 113510695A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J9/00—Programme-controlled manipulators
- B25J9/16—Programme controls
- B25J9/1602—Programme controls characterised by the control system, structure, architecture
- B25J9/1605—Simulation of manipulator lay-out, design, modelling of manipulator
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J9/00—Programme-controlled manipulators
- B25J9/16—Programme controls
- B25J9/1628—Programme controls characterised by the control loop
- B25J9/1651—Programme controls characterised by the control loop acceleration, rate control
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- Robotics (AREA)
- Mechanical Engineering (AREA)
- Automation & Control Theory (AREA)
- Feedback Control In General (AREA)
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Abstract
The invention provides a robot joint position control method, which comprises the following steps: establishing a Lagrange kinetic equation model of the robot joint; installing a first encoder and a second encoder at a joint of the robot, measuring position information of a motor end by using the first encoder, measuring position information of an output end of a speed reducer by using the second encoder, and calculating the speed of the motor according to the position information of the motor end; and outputting a signal to a position ring in a control loop, filtering a given signal of a speed ring, adjusting parameters of a notch filter according to the actual running condition of the joint, and filtering the given signal of the speed ring by adopting the notch filter so as to reduce the harmonic content of the signal.
Description
Technical Field
The invention relates to the technical field of industrial robots, in particular to a robot joint position control method.
Background
In recent years, with the increasing degree of automation, the application fields of robots have been developed from industries such as automobiles and machines to other application fields, and become an indispensable part of many industrial and commercial occasions. The robot joint contains a harmonic reducer, and the flexibility of the harmonic reducer causes the position precision to be reduced.
Although some control methods can solve the problems at present, the following defects exist: 1) the modeling compensation is carried out on the joint flexibility, but the flexible modeling of the speed reducer is difficult, and the flexible compensation effect is influenced. 2) Only a motor end encoder is installed, flexible compensation of the speed reducer is carried out through the observer, and the convergence time of the observer is too long. 3) Only the output encoder of the speed reducer is installed, so that the position precision is improved, and the bandwidth of a control loop is low.
Disclosure of Invention
The object of the present invention is to solve at least one of the technical drawbacks mentioned.
Therefore, the invention aims to provide a robot joint position control method.
In order to achieve the above object, an embodiment of the present invention provides a robot joint position control method, including the steps of: step S1, establishing a Lagrange kinetic equation model of the robot joint, wherein the Lagrange kinetic equation model of the robot joint is as follows:
wherein M ismIn order to obtain the inertia of the motor,
for motor end acceleration, DmIs the coefficient of sliding friction at the motor end,
as the motor end speed, fmIs the Coulomb friction coefficient at the motor end, τmApplying torque to the motor end, N being the reduction ratio of the reducer, K being the stiffness of the reducer, θmTo the motor end position, θLIs the position of the output end of the speed reducer,
the speed of the output end of the speed reducer is D, and the damping of the speed reducer is D;
step S2, installing a first encoder and a second encoder at the joint of the robot, and measuring the end position information theta of the motor by using the first encodermMeasuring the position information theta of the output end of the speed reducer by using a second encoderLCalculating the motor speed according to the position information of the motor end
And step S3, filtering the position loop output signal in the control loop, filtering the speed loop given signal, adjusting the parameters of a notch filter according to the actual running condition of the joint, and filtering the speed loop given signal by adopting the notch filter so as to reduce the harmonic content of the signal.
Further, performing characteristic analysis according to the established Lagrange dynamical equation model of the robot joint, wherein the characteristic analysis comprises the following steps: and solving a transfer function G _ M from the electromagnetic torque of the motor to the end position of the motor according to the set parameters, solving a transfer function G _ l from the electromagnetic torque of the motor to the output end position of the speed reducer, and testing the actual resonance frequency of the joint through a vibration analyzer.
Furthermore, the robot joint is controlled by a cascade PID three closed loop, and a current loop, a speed loop and a position loop are sequentially arranged from inside to outside.
Further, the position loop utilizes the low-frequency characteristic of a control system and adopts a load-side encoder to close the loop; the speed ring utilizes the high-frequency band characteristic of a control system and adopts the motor side to carry out closed loop.
Further, the filtering the speed loop given by using the notch filter includes:
acquiring a speed given signal, carrying out FFT analysis, observing harmonic content, adjusting the notch depth and notch width of a filter, and reducing the harmonic content of a preset frequency;
the joint operation noise is collected at the same time in the process of adjusting the parameters of the notch filter, the noise component different from the normal operation sound can be obviously heard, the noise component is gradually reduced by adjusting the parameters of the notch filter, when the noise component is obviously reduced to the extent that the noise component can not be heard by human ears, the control system does not diverge, the signal harmonic content of the preset frequency is reduced, and the adjustment of the parameters of the filter is stopped.
According to the robot joint position control method provided by the embodiment of the invention, double encoders are arranged at a robot joint, the position information of the motor end and the position information of the output end of the speed reducer are respectively measured, according to the system characteristics, the position loop is fed back to the closed loop through the position of the output end of the speed reducer, the speed loop is fed back to the closed loop through the speed of the motor, the bandwidth is improved, the input of the speed loop is filtered through a notch filter, and the harmonic component in a speed signal is reduced.
1) The method comprises the steps that a double encoder is installed on a robot joint, and position information of a motor end and position information of a speed reducer end are collected;
2) the control effect is improved through the position closed loop of the speed reducer and the speed closed loop of the motor, and two position feedback information are fully utilized for carrying out closed loop;
3) the precision is improved;
4) the harmonic content of the signal is reduced through the notch filter, and the joint noise performance is improved.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a flowchart of a robot joint position control method according to an embodiment of the present invention;
FIG. 2 is a block diagram of a robot joint control according to an embodiment of the present invention;
FIG. 3 is a bode diagram of transfer functions G _ M and G _ l according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
As shown in fig. 1 and 2, a robot joint position control method according to an embodiment of the present invention includes the steps of:
step S1, establishing a Lagrange dynamical equation model of the robot joint, wherein the Lagrange dynamical equation model of the robot joint is as follows:
wherein M ismIn order to obtain the inertia of the motor,
for motor end acceleration, DmIs the coefficient of sliding friction at the motor end,
as the motor end speed, fmIs the Coulomb friction coefficient at the motor end, τmApplying torque to the motor end, N being the reduction ratio of the reducer, K being the stiffness of the reducer, θmTo the motor end position, θLIs the position of the output end of the speed reducer,
the speed of the output end of the speed reducer and the damping of the speed reducer are D.
Specifically, the characteristic analysis is performed according to the established Lagrange dynamical equation model of the robot joint, and the characteristic analysis comprises the following steps: and solving a transfer function G _ M from the electromagnetic torque of the motor to the end position of the motor according to the set parameters, solving a transfer function G _ l from the electromagnetic torque of the motor to the output end position of the speed reducer, and testing the actual resonance frequency of the joint through a vibration analyzer.
Various parameters (different actual system parameters, which are only an example in the following) are set according to an actual system, and a transfer function G _ M from the electromagnetic torque of the motor to the end position of the motor and a transfer function G _ l from the electromagnetic torque of the motor to the output end position of the speed reducer are solved according to the set parameters.
The transfer function G _ M from the electromagnetic torque of the motor to the end position of the motor is as follows:
the transfer function G _ l from the electromagnetic torque of the motor to the position of the output end of the speed reducer is as follows:
then, a bode plot of G _ M, G _ l is drawn, as in FIG. 3. As can be seen from FIG. 3, the joint has resonance due to the flexibility, the resonance frequency is 16.7Hz, the actual resonance frequency of the joint is 12Hz when tested by the vibration analyzer, and the resonance frequency changes when the output end of the reducer is provided with different loads.
The robot joint is controlled by a cascade PID three closed loop, and a current loop, a speed loop and a position loop are sequentially arranged from inside to outside.
The position loop is low in bandwidth, and the low-frequency characteristic of a control system is mainly utilized, so that a load-side encoder is adopted for closed loop. The current loop bandwidth of the speed loop is high, the high-frequency band characteristic of a control system is mainly utilized, and the motor side is adopted for carrying out closed loop.
Step S2, installing a first encoder and a second encoder at the joint of the robot, and measuring the end position information theta of the motor by using the first encodermMeasuring the output end position of the reducer by using a second encoderSetting information thetaLAnd calculating the motor speed by differentiating the position of the motor end through the position information of the motor end
And step S3, filtering the position loop output signal in the control loop, filtering the speed loop given signal, adjusting the parameters of a notch filter according to the actual running condition of the joint, and filtering the speed loop given signal by adopting the notch filter so as to reduce the harmonic content of the signal.
The reduction ratio of the speed reducer is 100, one circle of the speed reducer end encoder generates 131072 pulses, and one circle of the motor end encoder generates 131072 pulses. When the motor speed is 3000rpm, the mechanical frequency of the motor is 50Hz, divided by the reduction ratio, the mechanical frequency of the output end of the speed reducer is 0.5Hz,
the position command updating period is 1ms, the increment of the position command of the speed reducer is 65.536 pulses and the increment of the position command of the speed reducer at the motor end is 6553.6 pulses in each updating period, the position information of the speed reducer is adopted for closed loop, and compared with the adoption of the position information for closed loop, the step amplitude of the position command of the motor is increased, the harmonic content of 1000Hz (related to the position command updating period) in the given speed ring is increased, and obvious noise is generated in the running process of the joint, so that the notch filter is adopted for filtering the given speed ring.
In step S3, the filtering process for the velocity loop specification using the notch filter includes:
acquiring a speed given signal, carrying out FFT analysis, observing harmonic content, adjusting the notch depth and notch width of a filter, and reducing the harmonic content of a preset frequency;
the joint operation noise is collected at the same time in the process of adjusting the parameters of the notch filter, the noise component different from the normal operation sound can be obviously heard, the noise component is gradually reduced by adjusting the parameters of the notch filter, when the noise component is obviously reduced to the extent that the noise component can not be heard by human ears, the control system does not diverge, the signal harmonic content of the preset frequency is reduced, and the adjustment of the parameters of the filter is stopped.
The preset frequency is 1000Hz for example:
the notch filter is primarily aimed at filtering out the 1000Hz signal in a given speed, determining the filter parameters mainly from two aspects. On the first hand, a speed given signal is collected, FFT analysis is carried out, the harmonic content of 1000Hz is observed, the notch depth and the notch width of a filter are adjusted, and the harmonic content is reduced. And in the second aspect, joint operation noise is collected simultaneously in the process of adjusting the parameters of the notch filter, noise components different from normal operation sound can be obviously heard, the noise components are gradually reduced by adjusting the parameters of the notch filter, when the noise components are obviously reduced to the extent that the noise components can not be heard by human ears, the control system does not diverge, the harmonic content of a 1000Hz signal is reduced, and the adjustment of the parameters of the filter is stopped.
According to the robot joint position control method provided by the embodiment of the invention, double encoders are arranged at a robot joint, the position information of the motor end and the position information of the output end of the speed reducer are respectively measured, according to the system characteristics, the position loop is fed back to the closed loop through the position of the output end of the speed reducer, the speed loop is fed back to the closed loop through the speed of the motor, the bandwidth is improved, the input of the speed loop is filtered through a notch filter, and the harmonic component in a speed signal is reduced.
1) The method comprises the steps that a double encoder is installed on a robot joint, and position information of a motor end and position information of a speed reducer end are collected;
2) the control effect is improved through the position closed loop of the speed reducer and the speed closed loop of the motor, and two position feedback information are fully utilized for carrying out closed loop;
3) the precision is improved;
4) the harmonic content of the signal is reduced through the notch filter, and the joint noise performance is improved.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (5)
1. A robot joint position control method is characterized by comprising the following steps:
step S1, establishing a Lagrange kinetic equation model of the robot joint, wherein the Lagrange kinetic equation model of the robot joint is as follows:
wherein M ismIn order to obtain the inertia of the motor,
for motor end acceleration, DmIs the coefficient of sliding friction at the motor end,
as the motor end speed, fmIs the Coulomb friction coefficient at the motor end, τmApplying torque to the motor end, N being the reduction ratio of the reducer, K being the stiffness of the reducer, θmTo the motor end position, θLIs the position of the output end of the speed reducer,
the speed of the output end of the speed reducer is D, and the damping of the speed reducer is D;
step S2, mounting at the joint of the robotA first encoder and a second encoder, the first encoder is used for measuring the position information theta of the motor endmMeasuring the position information theta of the output end of the speed reducer by using a second encoderLCalculating the motor speed according to the position information of the motor end
And step S3, filtering the position loop output signal in the control loop, filtering the speed loop given signal, adjusting the parameters of a notch filter according to the actual running condition of the joint, and filtering the speed loop given signal by adopting the notch filter so as to reduce the harmonic content of the signal.
2. The method for controlling a position of a robot joint according to claim 1, wherein in the step S1, the performing characteristic analysis according to the established lagrangian dynamical equation model of the robot joint comprises: and solving a transfer function G _ M from the electromagnetic torque of the motor to the end position of the motor according to the set parameters, solving a transfer function G _ l from the electromagnetic torque of the motor to the output end position of the speed reducer, and testing the actual resonance frequency of the joint through a vibration analyzer.
3. The method according to claim 1, wherein in step S1, the robot joint is controlled by a cascade PID three-closed loop, which includes a current loop, a speed loop, and a position loop from inside to outside.
4. A robot joint position control method according to claim 3, wherein the position loop is closed with a load side encoder using a low frequency characteristic of a control system; the speed ring utilizes the high-frequency band characteristic of a control system and adopts the motor side to carry out closed loop.
5. The robot joint position control method according to claim 1, wherein in the step S3, the filtering the velocity loop specification using the notch filter includes:
acquiring a speed given signal, carrying out FFT analysis, observing harmonic content, adjusting the notch depth and notch width of a filter, and reducing the harmonic content of a preset frequency;
the joint operation noise is collected at the same time in the process of adjusting the parameters of the notch filter, the noise component different from the normal operation sound can be obviously heard, the noise component is gradually reduced by adjusting the parameters of the notch filter, when the noise component is obviously reduced to the extent that the noise component can not be heard by human ears, the control system does not diverge, the signal harmonic content of the preset frequency is reduced, and the adjustment of the parameters of the filter is stopped.
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Cited By (2)
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| CN114488782A (en) * | 2022-04-18 | 2022-05-13 | 中国科学院西安光学精密机械研究所 | Turntable double-position ring control method and system based on harmonic speed reducing mechanism |
| WO2023227127A1 (en) * | 2022-05-27 | 2023-11-30 | 广东美的白色家电技术创新中心有限公司 | Control circuit and control method for joint module and robot |
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